PYRITE - The "Fools Gold" Stone

Lets start by how you may see Pyrite when looking for it. First it could be a 'cube' attached to a host rock, or a bunch of small 'crystals' in amoung other crystals such as Quartz, or maybe the real fooler, a Golden Pyrite "clump'. These are not the only way Pyrite appears however, as can be seen in several of the following pictures.

There are several shiny brassy yellow minerals, but pyrite is by far the most common and the most often mistaken for gold. Whether it is the golden look or something else, pyrite is a favorite among rock collectors. It can have a beautiful luster and interesting crystals. It is so common in the earth's crust that it is found in almost every possible environment, hence it has a vast number of forms and varieties. During their search for forture, many infamous shouts ocurred amid the Old West propsectors "There's Gold in that Riverbed !" only to be disappointed in finding Pyrite or as the golden rock quickly became known as "fools gold". Many a gold seaker was fooled by this shiny yellow mineral that looks so similar to gold.

Pyrite is a polymorph of Marcasite, which means that it has the same chemistry, FeS2, as Marcasite; but a different structure and therefore different symmetry and crystal shapes. Pyrite is difficult to distinguish from marcasite when a lack of clear indicators exists, as can be seen by the following picture of a piece of Marcasite.

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Almost any rock that looks a little rusty will mostly likely contain some pyrite. Pyrite is cubic crystals composed of iron sulfide; spherical and bulbous pyrites also exist; it is found in large quantities, mainly in coal mines and near clay workings. It comes in a vast number of forms and varieties, but the most common crystal shapes are cubic and octahedral.
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One sought-after form is flattened nodules found in chalk, siltstone and shale called “pyrite suns’ or ‘pyrite dollars’. These nodules are usually made from thin pyrite crystals radiating from the center.

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Enourmous amounts of small Pyrite crystal clusters come from Oruro and Colavi, Bolivia. In Navajun (Logroño), Spain, large cubic crystals, are abundant. They are frequently embedded in a light brown matrix, and are occasionally twinned.

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Perfect crystals occur in Rio Marina on the island of Elba, Italy. In the U.S., there are also many fine localities. In Park City, Bingham Co., Utah, very large, well shaped Pyritohedrons and Pyrite Cubes have been found, as well as in the American Mine in the Bingham Canyon, Salt Lake Co., Utah. Large, intergrown cubes, many times partially octahedral, occur in abundance at Leadville, Lake Co., Colorado. Pyrite "Dollars" are mostly found in Sparta, Randolph Co., Illinois. The French Creek Mine in Chester Co., Pennsylvania is famous for the octahedral crystals that occur there, although most are distorted. Many interesting nodules were recently discovered in Alden, Monroe Co., New York.

The use of Pyrite in decorations is also quite common. How many times have you visited a mine to see mining scenes in Pyrite avaiable on the sales counters.

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And more recently, Pyrite has been faceted so that it can be made into jewelry such as rings, pendants or earrings.

RAINBOW GEMSTONES - a variety of colors!

A play of words, a method of description, comparing something to a known item, a panarama of colors -- these all describe what are call "rainbows". Almost everyone knows what the "rainbow" in the sky after a thunderstom is and why it is present. But that same play of colors also describes several different kinds of gemstones. The following are several of the more commonly found gemstones with "rainbow" in their name.

A necklace with the major pieces being 'Rainbow' Agate

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An interesting piece of 'rainbow' Calsicila from Mexico.
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A pendant made from 'rainbow' Fluorite from Indiana.
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..A newer find called 'Rainbow' Pyrite from China..
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An old favorite among the lapidary community, 'rainbow' Obsidian.

An interesting piece of Chalcedony, that over the years has come to be know as the "rainbow" rock.

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MARCASITE - a Jewelry Trade Name misnomer !

The mineral Marcasite, many times called "white iron Pyrite" or "fools gold", is iron sulfide. Though Marcasite has the same chemical formula as Pyrite, it is a polymorph of Pyrite and crystalizes in a different crystal system, thereby making it a totally separate mineral. Marcasite (picture to right) is often mistakenly confused with Pyrite (picture below) but Marcasite is lighter and more brittle. Specimens of Marcasite often crumble and break up due to the unstable crystal structure, and it is this crystal structure that is the main difference between Marcasite and Pyrite.

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Marcasite can be formed as both a primary or a secondary mineral. As a primary mineral it forms nodules, concretions and crystals in a variety of sedimentary rock, where it forms as sharp individual crystals and crystal groups. As a secondary mineral it forms by chemical alteration of a primary mineral such as Chalcopyrite. On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife.

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Marcasite may go through a condition known as "Pyrite decay", in which a specimen slowly disintegrates into a white powder. When a specimen goes through pyrite decay, the marcasite reacts with moisture in the air, the sulfur combining with water to produce sulfuric acid that attacks other sulfide minerals. It is unsafe to have around at this point.

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The Marcasite/Pyrite polymorph pair is probably the most famous polymorph pair next to the Diamond/Graphite pair. Adding to the confusion between Marcasite and Pyrite is the use of the word "Marcasite" as a 'Jewelry Trade Name'. The term is applied to small polished and faceted stones, usually Pyrite that are inlayed in sterling silver and sometime platenium with black rhodium highlighting the stones. But even though the jewelry trade refers to these small stones as "Marcasite", they are actually small pieces of Pyrite. In jewelry, Pyrite is used as the gemstone and is improperly termed "Marcasite" following the misnomer of the trade name. True Marcasite is never used as a gemstone in settings due to its brittle and chemically unstable structure.

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Pendants of Sterling Silver with "Marcasite (Pyrite)" stones as highlights
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For collectors pieces of Marcasite are prized in a collection. But they must be kept sealed in air tight containers so that they do not break down and become a pile of white powder. Miners, however, often viewed Pyrite and Marcasite negatively since they had a deceptive appearance, which many mistook for gold. Many based their opinions on where to dig or pan based on pieces of these minerals being in the ground or water, and too late learned that these stones were worthless. Thusly they inherited the name "fool’s gold".
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QUARTZ with "Inclusions"

Pieces of 'Clear Quartz' with inclusions can be a facinating study. I am not about to attempt to list or go into the many types of inclusions that can occur in Quartz, because for each one I mention, someone will be able to name a dozen more. For the purpose of this article we will talk about 'Rutilated Quartz', 'Dendritic Quartz' and 'Tourmalinated Quartz'. I will also present some pictures I have been provided of some other interesting included Quartz pieces.
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A piece of clear crystal Quartz known as a Sceptor.

Dendritic Quartz. The stains are found in microscopic fissures that cause them to branch out like tree limbs or fern like inclusions. Of course in nature no two things are alike, making each gem one of a kind. Like most of the included quartz, the primary sources of Dendritic Quartz are Brazil and Africa, but some have been found in the western United Satates and Arkansas.

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Rutilated Quartz. Rutile is a major ore of titanium, which is a metal used for high tech alloys. It often forms needle-like crystal inclusions inside the Quartz crystal. This form of quartz looks like small bars of imbedded gold. Rutile is a 6 on the Mohs scale whereas Quartz is a 7. Because of the difference in hardness between the two materials and because of the way rutile forms inside, this can be a difficult stone to attain a smooth surface without pits. Most Rutilated Quartz is found is Brazil, Pakistan, Kazakhstan, Madagascae, Brazil and several locations in the United States.

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Tourmalinated Quartz. As pointed out many minerals may be found as inclusions in quartz. When Tourmaline is found within quartz, the quartz is known as "tourmalinated". Most of this variety of Quartz is found in Brazil but large pockets have also been found in California.

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Here are some pictures of some other types of included Quartz.

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Quartz with included Pyrite........ Quartz with included Gilalite

Quartz with included Lepidocrocite and Hematite

Lodolite is a term used for a varity of Quartz with included minerals from Minas Gerais, Brazil. The colorations and patterns come from three main types of minerals, Chlorite, Iron, and Calcite.

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